1. Field of the Invention:
The present invention relates generally to an air-conditioner for automobiles, and more particularly to an automobile air-conditioner incorporating a cooled air bypass unit for controlling the temperature of an upper part of the vehicle passenger compartment in the vicinity of the head of an occupant.
2. Description of the Prior Art:
Cooled air bypass units are conventionally used in an automobile air-conditioner for lowering the temperature of air in the vicinity of the head of an occupant of an automobile while the automobile is running in the sun. According to Japanese Utility Model Publication No. 59-34497 and Japanese Utility Model Laid-open Publication No. 60-151710, a main air-flow duct has an opening at a position immediately downstream of an evaporator, a cooled air bypass door disposed at the opening to open and close the opening, and a cooled air bypass duct provided separately from the main air-flow duct and connected at its one end to the opening, the other end of the cooled air bypass duct being connected to a vent opening or solely constituting an upper opening facing toward the face of the occupant. With this arrangement, the head of the occupant can be cooled while the automobile is running in the sun, and more particularly when the solar radiation becomes maximum, so that the air-conditioning feeling can be improved.
The opening and closing operation of the bypass door of the known cooled air bypass unit is controlled depending on the vehicle passenger compartment temperature or the solar radiation quantity. However, since the control of the bypass door is performed independently of the control of other component of the air-conditioner, the desired cooling effect can be obtained only when the amount of bypassed cooled air is fairly large (about 50%) relative to the amount of main airflow which is controlled by a total control signal.
As the internal space of an instrument panel of the automobile is narrowed by other necessary parts, for example, components of the main air-flow duct, there is no room available for the installation of a relatively large cooled air bypass duct capable of providing a sufficient amount of bypassed cooled air. In practice, the amount of bypassed cooled air is only about 10% of the total amount of air discharge into the passenger compartment and hence a sufficient cooling of the head of the occupant is difficult to achieve.